首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1300篇
  免费   41篇
  国内免费   1篇
电工技术   16篇
综合类   1篇
化学工业   167篇
金属工艺   11篇
机械仪表   22篇
建筑科学   20篇
矿业工程   1篇
能源动力   17篇
轻工业   202篇
水利工程   4篇
石油天然气   8篇
无线电   57篇
一般工业技术   101篇
冶金工业   623篇
自动化技术   92篇
  2024年   5篇
  2023年   7篇
  2022年   16篇
  2021年   33篇
  2020年   20篇
  2019年   39篇
  2018年   29篇
  2017年   43篇
  2016年   32篇
  2015年   25篇
  2014年   36篇
  2013年   51篇
  2012年   47篇
  2011年   62篇
  2010年   43篇
  2009年   39篇
  2008年   33篇
  2007年   22篇
  2006年   22篇
  2005年   27篇
  2004年   22篇
  2003年   18篇
  2002年   12篇
  2001年   10篇
  2000年   5篇
  1999年   23篇
  1998年   177篇
  1997年   116篇
  1996年   65篇
  1995年   50篇
  1994年   41篇
  1993年   41篇
  1992年   12篇
  1991年   11篇
  1990年   8篇
  1989年   9篇
  1988年   3篇
  1987年   10篇
  1986年   8篇
  1985年   4篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1978年   3篇
  1977年   16篇
  1976年   31篇
  1975年   2篇
  1965年   1篇
  1955年   1篇
排序方式: 共有1342条查询结果,搜索用时 15 毫秒
951.
Monolayer spreads of cervical cells were prepared and reacted in sequence with two fluorescent probes. The nuclei were reacted with 4,6-Diamidino-2-phenylindole (DAPI), resulting in white fluorescence of all cell nuclei. Those cells possessing active guanidinobenzoatase (GB) bound the second probe, rhodamine-alpha-N-agmatine (Rh-Agm), resulting in orange cell surface fluorescence. Atypical epithelial cells possessed both active GB and enlarged nuclei; such cells could easily be recognised by their cytological appearance. We illustrate our results in the form of colour prints which are representative of our observations of cells in both normal and abnormal cervical spreads.  相似文献   
952.
953.
The BRCA1 gene on human chromosome 17q21 is responsible for an autosomal dominant syndrome of inherited early onset breast/ovarian cancer. It is estimated that women harboring a germline BRCA1 mutation incur an 85% lifetime risk of breast cancer and a greatly elevated risk of ovarian cancer. The BRCA1 gene has recently been isolated and mutations have been found in the germline of affected individuals in linked families. Previous studies of loss of heterozygosity (LOH) in breast tumors have been carried out on sporadic tumors derived from individuals without known linkage to BRCA1 and on tumors from linked families. Loss of large regions of chromosome 17 has been observed, but these LOH events could not be unequivocally ascribed to BRCA1. We have studied 28 breast and 6 ovarian tumors from families with strong evidence for linkage between breast cancer and genetic markers flanking BRCA1. These tumors were examined for LOH using genetic markers flanking and within BRCA1, including THRA1, D17S856, EDH17B1, EDH17B2, and D17S183. Forty-six percent (16/34) of tumors exhibit LOH which includes BRCA1. In 8 of 16 tumors the parental origin of the deleted allele could be determined by evaluation of haplotypes of associated family members; in 100% of these cases, the wild-type allele was lost. In some of these families germline mutations in BRCA1 have been determined; analyses of tumors with LOH at BRCA1 have revealed that only the disease-related allele of BRCA1 was present. These data strongly support the hypothesis that BRCA1 is a tumor suppressor gene.  相似文献   
954.
A study was conducted on 40 Mycobacterium fortuitum strains isolated from symptomatic patients suffering from respiratory diseases and skin lesions. Their susceptibility to different antimicrobial agents was determined by the broth microdilution method, measuring minimal inhibitory concentration. There was sensitivity of the strains to gentamicin and tetracycline as well as resistance to the tuberculostatic drugs used (isoniazid and ethambutol) and cefalotin.  相似文献   
955.
BACKGROUND: Linxian, China, has one of the highest rates of esophageal cancer in the world. Other authors have described high prevalences of histologic esophagitis, atrophy, and dysplasia in Linxian and have suggested that these findings may represent precancerous lesions in this population. In 1987, a new endoscopic survey allowed the authors to make an independent study of esophageal histology in Linxian. METHODS: There were 1567 satisfactory squamous esophageal biopsies available from 754 patients. These biopsies were classified as normal, atrophy, acanthosis, esophagitis, squamous dysplasia, or squamous cancer. RESULTS: Classified by their worst diagnosis, 56.5% of the 754 patients had normal mucosa, 0.0% atrophy, 11.5% acanthosis, 4.6% esophagitis, 22.7% squamous dysplasia, and 4.6% squamous cancer. CONCLUSIONS: The results show a different distribution of esophageal squamous diagnoses than has been reported previously from this population. The authors believe that the major reason for this discrepancy was differences in histologic criteria. In this survey, seemingly small differences in criteria could cause large differences in apparent disease prevalence; this was especially true for esophagitis. By the criteria used in this study, histologic esophagitis and atrophy are uncommon findings in Linxian, raising questions about their significance as precursor lesions of esophageal cancer in this population.  相似文献   
956.
957.
958.
The effects of RbCl and CsCl on voluntary intake of ethanol solution by rats preferring ethanol solution 5% (w/w) over water as the drinking fluid was studied as a function of the dose given and the vehicle injected. Administration of RbCl or CsCl, 0.5 mEq/kg/day or 1.5 mEq/kg/day for three consecutive days, did not alter amounts of ethanol consumed. Repeated administration of RbCl or CsCl, 3.0 mEq/kg/day for three days, produced some moderate reduction in ethanol consumption. Simultaneous injection of RbCl (1.5 mEq/kg) and CsCl (1.5 mEq/kg) resulted in greater and profound lasting decrease in ethanol drinking. The later treatment did not alter specific activities of rat liver alcohol- and aldehyde dehydrogenase from saline treated controls. In general, dissolving the chloride salt of the alkali metals in saline resulted in greater effects on ethanol drinking than that determined after identical dose injected with water as the vehicle. The possible mechanism(s) underlying the effects of alkali metal salts used are suggested.  相似文献   
959.
960.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号